The present invention is directed to object-sensor-based automatic flow controllers. It applies particularly to optical-radiation emitters and sensors used in such controllers.
Object-sensor-based automatic flow controllers, such as automatic faucets, control fluid flow in response to object detection within a target region. Such systems work best if the object sensor is reasonably discriminating. While an automatic faucet should respond to a user's hands, for instance, it should not respond to the sink at which the faucet is mounted. Among the ways of making the system discriminate between the two is to limit the target region in such a manner as to exclude the sink's location.
One way to make the target region exclude the sink's location is to mount the sensor circuitry's optical-radiation emitter and receiver on the faucet spout near its outlet. Then the emitter power and/or receiver sensitivity can be so limited as to restrict the sensor's range to less than the outlet-to-sink distance. But it is sometimes considered undesirable esthetically or for other reasons to mount the emitter and receiver near the end of the spout. In such cases, discrimination by range alone is often impractical, because the emitter and receiver must ordinarily be mounted at a distance from the spout that is comparable to their distance from a sink surface to be excluded. So the beam width of the emitter and/or receiver is so limited as to exclude the unwanted target.
Although this approach can yield a serviceable system, the resultant position sensitivity usually makes it less convenient: the user must often make an effort to position his hands properly. Also, the lenses conventionally used to limit beam width exact a cost penalty.